As a conventional technique, there is a known apparatus for, while rotating a wafer, detecting and accumulating edge positions of the wafer in association with the rotational angles, calculating an eccentricity amount and direction of the wafer position according to a largest value and a smallest value of detection signals, and centering the wafer according to the eccentricity data, wherein, since the edge positions change more sharply at a start point and an end point of a flat portion or the like provided on the wafer than at the other portions, this apparatus sets the flat portion or the like at a specific position relative to another stage such as a transfer apparatus, by calculating a rate of change in the edge position data reaching at least a certain level. See, for example, Japanese Patent No. 2729297 at page 1 and FIG. 1.
For example, if a workpiece positioned using this sort of conventional apparatus is transferred by a workpiece transfer apparatus to an apparatus for performing chemical vapor deposition (CVD), chemical mechanical polishing (CMP), or the like, the workpiece can undergo desired processing as appropriate.
If a workpiece such as a wafer in which burrs, chipping, or the like has occurred at the edge is subjected to processing such as CVD or polishing, the workpiece may be damaged by heat, pressure, or the like applied to the workpiece. Accordingly, it is preferable to perform inspection for detecting whether or not there is a defect such as burrs or chipping, before performing the processing on the workpiece. For this purpose, first, it is desirable to perform defect inspection on the workpiece before positioning the workpiece using such a conventional technique as described above.
However, in the case of performing defect inspection on the workpiece, the workpiece has to be once transferred by a workpiece transfer apparatus to a defect inspection apparatus and be subjected to defect inspection, and, after the inspection, the workpiece has to be transferred by the workpiece transfer apparatus to a workpiece positioning apparatus and be subjected to positioning. That is, there is a problem in which it takes time to perform inspection on the workpiece and to transfer the workpiece to and from the inspection apparatus.
There are further problems in which the cost increases because the inspection apparatus has to be provided in addition to the positioning apparatus, and in which saving the space is difficult because an installation location of the inspection apparatus has to be secured on a workpiece transfer path.
As a result, the conventional technique is problematic in that it is not possible to perform defect detection on a workpiece as appropriate.